Business getting over big blow -- it's used to strain (8)
I believe the answer is:
colander
'used to strain' is the definition.
I can't judge whether this definition defines the answer.
'business getting over big blow' is the wordplay.
'business' becomes 'co'.
'getting' is a charade indicator (letters next to each other).
'over big blow' becomes 'lander' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'co'+'lander'='COLANDER'
'it's' is the link.
Can you help me to learn more?
(Other definitions for colander that I've seen before include "Culinary strainer" , "Boiled 20 Down may be strained through this" , "kitchen utensil" , "It is used to strain water from food" , "Food strainer" .)